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© 1991-2002 Jerry Emanuelson GREEN TEA POLYPHENOLS
In ordinary language, tea is often used to mean any beverage produced from the leaf of any plant. Technically, tea comes from the leaf of one particular plant. The same plant is the source of green tea, as well as the black tea that is much more popular in the U.S. Tea is more widely consumed than any beverage in the world other than water. Most tea consumed is black tea, which is produced by a process which oxidizes the green leaf. This process enhances the taste, but destroys most of an important class of chemicals called green tea polyphenols (GTP). GTP has been widely studied in recent years and appears to be an important substance for the chemoprevention of cancer. In March, 1991 an important medical conference on green tea was held in New York, The First International Symposium on the Physiological and Pharmacological Effect of Camellia Sinensis (Tea). Titles of some of the reports presented at that symposium included:
(The summaries of these papers were published in Preventive Medicine 21, pp.331-333, 1992) Report 3 found no adverse effects of tea on kidney function except for a very few persons with terminal kidney diseases. The other reports showed very positive effects for tea extracts. A number of complete reports on Green Tea Polyphenols were published in subsequently published in Preventive Medicine during 1992 showing the beneficial effects of green tea on cancer and coronary artery disease. A report in the October, 1992 issue of Comprehensive Therapy (pp. 3-8) "Green Tea in the Chemoprevention of Cancer," covered the effectiveness of GTP in preventing a wide variety of cancers. The cancers that GTP can prevent in humans include the deadliest cancers such as those of the liver, lungs, colon, and pancreas. In addition, green tea has been show to be very effective at preventing tooth decay and killing some types of stomach viruses. Green Tea Polyphenols are present in commercially available green teas such as the Lipton's Green Tea sold in most grocery stores and other brands sold in health food stores. Oolong tea is partially oxidized green tea and contains about 20-30 percent of the GTP concentration of green tea. Green and black teas may also be mixed to obtain both the flavor of black tea and the health benefits of green tea. Green Tea Extract capsules containing 20 percent to 80 percent Green Tea Polyphenols are available from several supplement manufacturers. The optimal daily dose of Green Tea Polyphenols is not yet known. Commercially available GTP capsules are typically equivalent to five or more cups of tea, yet even one cup of green tea daily seems to confer some benefit. Ideally, however, Green Tea Polyphenols should be consumed several times a day since the lifetime of Green Tea Polyphenols in the body is very short. All tea contains oxalates that may cause kidney stones. The most common type of kidney stone is the calcium oxalate stone formed in the kidney when soluble oxalates combine with soluble calcium compounds to form the highly-insoluble calcium oxalate. The probability of tea causing kidney stones can be dramatically reduced by ingesting some form of calcium along with the tea in order to form the calcium oxalate in the digestive tract (where it cannot be absorbed and will pass through), rather than in the kidney. (An additional warning for sufferers of kidney stones: The food with the highest oxalate content is spinach. Spinach contains so much oxalate that spinach processing equipment sometimes gets clogged up with insoluble oxalates.) Next Chapter: NANOTECHNOLOGY & CRYONICS |